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Merge pull request #5568 from rogermb/jpeg2000-resolution

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Add support for reading DPI information from JPEG2000 images
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Andrew Murray 2021-08-03 00:06:13 +10:00 committed by GitHub
commit 6406dabf29
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6 changed files with 136 additions and 41 deletions
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24
Tests/test_file_jpeg2k.py
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@ -4,7 +4,7 @@ from io import BytesIO
import pytest
from PIL import Image, ImageFile, Jpeg2KImagePlugin, features
from PIL import Image, ImageFile, Jpeg2KImagePlugin, UnidentifiedImageError, features
from .helper import (
assert_image_equal,
@ -151,6 +151,28 @@ def test_reduce():
assert im.size == (40, 30)
def test_load_dpi():
with Image.open("Tests/images/test-card-lossless.jp2") as im:
assert im.info["dpi"] == (71.9836, 71.9836)
with Image.open("Tests/images/zero_dpi.jp2") as im:
assert "dpi" not in im.info
def test_header_errors():
for path in (
"Tests/images/invalid_header_length.jp2",
"Tests/images/not_enough_data.jp2",
):
with pytest.raises(UnidentifiedImageError):
with Image.open(path):
pass
with pytest.raises(OSError):
with Image.open("Tests/images/expected_to_read.jp2"):
pass
def test_layers_type(tmp_path):
outfile = str(tmp_path / "temp_layers.jp2")
for quality_layers in [[100, 50, 10], (100, 50, 10), None]:

153
src/PIL/Jpeg2KImagePlugin.py
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@ -6,6 +6,7 @@
#
# History:
# 2014-03-12 ajh Created
# 2021-06-30 rogermb Extract dpi information from the 'resc' header box
#
# Copyright (c) 2014 Coriolis Systems Limited
# Copyright (c) 2014 Alastair Houghton
@ -19,6 +20,79 @@ import struct
from . import Image, ImageFile
class BoxReader:
"""
A small helper class to read fields stored in JPEG2000 header boxes
and to easily step into and read sub-boxes.
"""
def __init__(self, fp, length=-1):
self.fp = fp
self.has_length = length >= 0
self.length = length
self.remaining_in_box = -1
def _can_read(self, num_bytes):
if self.has_length and self.fp.tell() + num_bytes > self.length:
# Outside box: ensure we don't read past the known file length
return False
if self.remaining_in_box >= 0:
# Inside box contents: ensure read does not go past box boundaries
return num_bytes <= self.remaining_in_box
else:
return True # No length known, just read
def _read_bytes(self, num_bytes):
if not self._can_read(num_bytes):
raise SyntaxError("Not enough data in header")
data = self.fp.read(num_bytes)
if len(data) < num_bytes:
raise OSError(
f"Expected to read {num_bytes} bytes but only got {len(data)}."
)
if self.remaining_in_box > 0:
self.remaining_in_box -= num_bytes
return data
def read_fields(self, field_format):
size = struct.calcsize(field_format)
data = self._read_bytes(size)
return struct.unpack(field_format, data)
def read_boxes(self):
size = self.remaining_in_box
data = self._read_bytes(size)
return BoxReader(io.BytesIO(data), size)
def has_next_box(self):
if self.has_length:
return self.fp.tell() + self.remaining_in_box < self.length
else:
return True
def next_box_type(self):
# Skip the rest of the box if it has not been read
if self.remaining_in_box > 0:
self.fp.seek(self.remaining_in_box, os.SEEK_CUR)
self.remaining_in_box = -1
# Read the length and type of the next box
lbox, tbox = self.read_fields(">I4s")
if lbox == 1:
lbox = self.read_fields(">Q")[0]
hlen = 16
else:
hlen = 8
if lbox < hlen or not self._can_read(lbox - hlen):
raise SyntaxError("Invalid header length")
self.remaining_in_box = lbox - hlen
return tbox
def _parse_codestream(fp):
"""Parse the JPEG 2000 codestream to extract the size and component
count from the SIZ marker segment, returning a PIL (size, mode) tuple."""
@ -53,55 +127,45 @@ def _parse_codestream(fp):
return (size, mode)
def _res_to_dpi(num, denom, exp):
"""Convert JPEG2000's (numerator, denominator, exponent-base-10) resolution,
calculated as (num / denom) * 10^exp and stored in dots per meter,
to floating-point dots per inch."""
if denom != 0:
return (254 * num * (10 ** exp)) / (10000 * denom)
def _parse_jp2_header(fp):
"""Parse the JP2 header box to extract size, component count and
color space information, returning a (size, mode, mimetype) tuple."""
"""Parse the JP2 header box to extract size, component count,
color space information, and optionally DPI information,
returning a (size, mode, mimetype, dpi) tuple."""
# Find the JP2 header box
reader = BoxReader(fp)
header = None
mimetype = None
while True:
lbox, tbox = struct.unpack(">I4s", fp.read(8))
if lbox == 1:
lbox = struct.unpack(">Q", fp.read(8))[0]
hlen = 16
else:
hlen = 8
if lbox < hlen:
raise SyntaxError("Invalid JP2 header length")
while reader.has_next_box():
tbox = reader.next_box_type()
if tbox == b"jp2h":
header = fp.read(lbox - hlen)
header = reader.read_boxes()
break
elif tbox == b"ftyp":
if fp.read(4) == b"jpx ":
if reader.read_fields(">4s")[0] == b"jpx ":
mimetype = "image/jpx"
fp.seek(lbox - hlen - 4, os.SEEK_CUR)
else:
fp.seek(lbox - hlen, os.SEEK_CUR)
if header is None:
raise SyntaxError("could not find JP2 header")
size = None
mode = None
bpc = None
nc = None
dpi = None # 2-tuple of DPI info, or None
unkc = 0 # Colorspace information unknown
hio = io.BytesIO(header)
while True:
lbox, tbox = struct.unpack(">I4s", hio.read(8))
if lbox == 1:
lbox = struct.unpack(">Q", hio.read(8))[0]
hlen = 16
else:
hlen = 8
content = hio.read(lbox - hlen)
while header.has_next_box():
tbox = header.next_box_type()
if tbox == b"ihdr":
height, width, nc, bpc, c, unkc, ipr = struct.unpack(">IIHBBBB", content)
height, width, nc, bpc, c, unkc, ipr = header.read_fields(">IIHBBBB")
size = (width, height)
if unkc:
if nc == 1 and (bpc & 0x7F) > 8:
@ -114,11 +178,10 @@ def _parse_jp2_header(fp):
mode = "RGB"
elif nc == 4:
mode = "RGBA"
break
elif tbox == b"colr":
meth, prec, approx = struct.unpack_from(">BBB", content)
if meth == 1:
cs = struct.unpack_from(">I", content, 3)[0]
meth, prec, approx = header.read_fields(">BBB")
if meth == 1 and unkc == 0:
cs = header.read_fields(">I")[0]
if cs == 16: # sRGB
if nc == 1 and (bpc & 0x7F) > 8:
mode = "I;16"
@ -128,7 +191,6 @@ def _parse_jp2_header(fp):
mode = "RGB"
elif nc == 4:
mode = "RGBA"
break
elif cs == 17: # grayscale
if nc == 1 and (bpc & 0x7F) > 8:
mode = "I;16"
@ -136,18 +198,27 @@ def _parse_jp2_header(fp):
mode = "L"
elif nc == 2:
mode = "LA"
break
elif cs == 18: # sYCC
if nc == 3:
mode = "RGB"
elif nc == 4:
mode = "RGBA"
elif tbox == b"res ":
res = header.read_boxes()
while res.has_next_box():
tres = res.next_box_type()
if tres == b"resc":
vrcn, vrcd, hrcn, hrcd, vrce, hrce = res.read_fields(">HHHHBB")
hres = _res_to_dpi(hrcn, hrcd, hrce)
vres = _res_to_dpi(vrcn, vrcd, vrce)
if hres is not None and vres is not None:
dpi = (hres, vres)
break
if size is None or mode is None:
raise SyntaxError("Malformed jp2 header")
raise SyntaxError("Malformed JP2 header")
return (size, mode, mimetype)
return (size, mode, mimetype, dpi)
##
@ -169,7 +240,9 @@ class Jpeg2KImageFile(ImageFile.ImageFile):
if sig == b"\x00\x00\x00\x0cjP \x0d\x0a\x87\x0a":
self.codec = "jp2"
header = _parse_jp2_header(self.fp)
self._size, self.mode, self.custom_mimetype = header
self._size, self.mode, self.custom_mimetype, dpi = header
if dpi is not None:
self.info["dpi"] = dpi
else:
raise SyntaxError("not a JPEG 2000 file")